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BRAD Pitt and Angelina Jolie have stepped out together at the premiere of zombie thriller World War Z - Jolie's first public appearance since announcing last month that she had undergone a double mastectomy.

The couple walked a black, rather than red, carpet at the world premiere overnight of the big-budget film, which stars Pitt as a United Nations employee battling to save the world.

The pair wore complementary black outfits as they signed autographs for fans in Leicester Square.

Speaking to reporters outside the premiere, Jolie said she "felt great" and was "very happy to see the discussion about women's health expanded and that means the world to me."

Jolie revealed last month that she had had her breasts removed after discovering she has an inherited genetic mutation that puts her at high risk of breast and ovarian cancer.

Jolie's mother Marcheline Bertrand died from ovarian cancer at 56, and the actress' aunt Debbie Martin, 61, died of breast cancer last month.

The actress also thanked all those who supported her during and since the surgery while Pitt hailed her for her bravery and act of selflessness, admitting he got emotional just thinking about it.

He told the BBC the experience had certainly made their family stronger.

"What it means to others has really surprised me," he said. "The beautiful thing is that for us, life will go on. ... It certainly brought our family tighter together."

Her appearance at the star-studded event came as it emerged Jolie missed her aunt's funeral so she could join her partner and "support Brad" at the premiere.